Portable humidifier



FIG. 1 is a front perspective view of a portable humidifier showing my new design;

FIG. 2 is a side elevation view thereof on a reduced scale, the opposite side being a mirror image of that shown;

FIG. 3 is a rear elevation view thereof on a reduced scale; and

FIG. 4 is a bottom plan view thereof on a reduced scale. 

The ornamental design for a portable humidifier, as shown and described. 